Features of faults in the central and northern Tibetan plateau based on results of INDEPTH (III)-MT

Abstract

The features of the faults in the central and northern Tibetan plateau are discussed, based on two super-wide band magnetotelluric (MT) sounding profiles belonging to the INDEPTH (III)-MT project, which were finished between 1998 and 1999: one is from Deqing to Longweicuo (named line 500), the other is from Naqu to Golmud (line 600). This work assists research on the collision and subduction mode between the India and Asia plates. The MT results show that there is a series of deep faults, F1 to F10, in the central and northern Tibetan plateau. Of these faults, F2 is an earlier main fault which leans to the north, and F1 is a later main overriding fault. The Jiali deep fault zone, which has a very complex space structure, is composed of these two faults. F3, F4 and F5 are super-deep faults. They are high-angle faults and lean a little to the south. The main fault zone of the BangongNujiang suture is composed of these three faults. Because of later activity in the structure, several shallow faults formed in the upper crust within the Bangong-Nujiang suture. The Tanggula fault zone is composed of two main faults, F6 and F7, and a series of sub-faults. The shallow segments of the main faults are in high angles and the deep segments of main faults are in low angles. These two faults generally lean to the south and extend into the lower crust. The Jinshajiang suture is composed of the Jinshajiang fault (F8) and the Kekexili fault (F9), and there is a series of sub-faults in the upper crust between these two faults. The Jinshajiang suture is a very wide suture caused by continent-continent collision. The Middle Kunlun fault (F10), which is the main structure of the Kunlun fault zone, is a high angle, super-deep fault. It is the north boundary of the Songpan-Ganzi-Kekexili block. Based on the conductive structure of the profile, the southern part of the Middle Kunlun fault belongs to the Tibetan plateau, but it is not certain whether the northern part of the Middle Kunlun fault belongs to the Tibetan plateau. There are conductive bodies stretching from the crust into the upper mantle below the Bangong-Nujiang suture and Jinshajiang suture. This may suggest heat exchange between the crust and mantle.

Conductivity structure and rheological property of lithosphere in Southern Tibet inferred from super-broadband magnetotelluric sounding

“…These data suggest that the crust of Southern Tibet contains layers of partial melting or hot fluids which cause anomalies of high-conductivity [2,7].…”

“…By 1997, three super-broadband (320-0.00005 Hz) MT profiles were completed, which are Yatung-Xoggola (line 100), Taktse-Bamucuo (line 200), and Xoggola-Damshung (line 300) [2][3][4]. The subsequent INDETH (III)-MT in 1998 and 1999 completed another two profiles, i.e., Dechen-Longweico (line 500) and NakchuGolmud (line 600) [5][6][7].…”

Seismic reflection and magnetotelluric profiles across the Luobusa ophiolite: Evidence for the deep structure of the Yarlung Zangbo suture zone, southern Tibet

“…5d has been discussed in past MT surveys. The west-east profiles crossing the Yarlung Zangbo River include the Gyirong-Coqênn profile, the Tingri-Comai profile, the Yadong-Guxuela profile, and the Cona-Medro Gongkar profile (Zhao et al, 2008;Tan et al, 2004Tan et al, , 2006Wei et al, 2007Wei et al, , 2010; the MT profile crossing the Luobusa ophiolite in this paper is closest to the Cona-Medro Gongkar profile. Observation carried out in the mine area revealed basically the same electrical conductivity structures as those found from the study of the above profiles, but we choose to present finer images because of more densely distributed observation stations.…”

Electrical Structure of the Middle Segment of the Tancheng‐Lujiang Fault Zone and Its Geological Implications

“…Thus there must be conspicuous electric gradient or distortion belts around fault zones. In general, the extending direction of gradient zones featured by dense contours (or zones of distorted contours) on a cross section of resistivity indicates the general dip of the fault, and their lower ends denote the cutting depth of the fault [10] . Thus we can infer the major faults and their dips and cutting depths of the central TL fault zone based on the resistivity model along the Tai'an-Rizhao profile.…”